How I got Acme to renew my Ghost blog's SSL cert

SSL renewal via Acme was mysteriously failing. It reported Verify error detail:...hex... Invalid response from ...uri.... After trying various commands, I found that I needed to run ghost setup nginx (even though Nginx was "already setup" and working fine), do sudo su to run as root, then the Acme command: "/etc/letsencrypt"/ --cron --home "/etc/letsencrypt" --log. This successfully updated the certificate.